Studies have been designed to investigate the effects of narcotic analgesics on brain amine levels and neuroendocrine function. The levels and turnover of brain amines (norepinephrine, dopamine, serotonin, acetylcholine) will be correlated with some parameters of anterior pituitary activity (adrenocorticotropin, thyrotropin and growth hormone secretion) following the acute and chronic administration of narcotic analgesics. Also, localization of the central sites and pathways of these agents will be determined by the injection of microquantities of the drugs into specific brain sites, while using an endocrine response for an endpoint.